Paper Title

BACKGROUND: Recently hypoxic training has gained popularity as a method to support traditional forms of exercise. With the advancement of technology and the ability to simulate artificial high-altitude conditions, innovative training models have been developed, such as "live high-train low" (LHTL) and "live low-train high" (LLTH). Current reports suggest that exposure to hypoxia has a positive impact on physical fitness and body composition. However, due to difficulties in organizing studies that would involve participants' prolonged exposure to hypoxic conditions, there is still a lack of reliable reports comparing the effectiveness of LLTH and LHTL strategies. PURPOSE: The aim of the study was to compare the effect of a 4-week high-intensity interval training (HIIT) under hypoxic conditions on somatic indicators and aerobic endurance in non-athletic men. MATERIALS and METHODS: The study involved 28 healthy, non-athletic men aged 19-27 (mean = 22.33; SD = 4.48). Participants were randomly assigned to three groups, each consisting of 9 individuals:LLTH (living in normoxia, training in normobaric hypoxia), LHTL (living in normobaric hypoxia, training in normoxia), and C (no training intervention). Participants trained on a cycle ergometer three times a week for four weeks (12 training sessions in total). Each training session consisted of a 15-minute warm-up (10 minutes of continuous cycling at 90W load and 5 minutes of stretching), the main part (30 minutes of interval training: 15x45s progressive work from 75 to 90% WRmax / 75s rest, load 90W), and a 10-minute cool down (continuous cycling at 70W load and 5 minutes of stretching). Participants trained in a hypoxic chamber simulating an altitude of 3,000m above sea level at FiO2 (fraction of inspired oxygen) of 14%, temperature of 21°C, and humidity of 50%. Before and after the intervention, measurements of selected somatic indicators (BH [cm] – body height, BM [kg] – body mass) were taken, based on which the body mass index (BMI [kg/m2]) was calculated, body composition analysis (FFM [kg] – fat-free mass, FM[kg] - fat mass) was performed, and maximal oxygen consumption (VO2max [L/min], [ml/min/kg]), maximum heart rate (HRmax [bpm]), and maximum pulmonary ventilation (VEmax [L/min]) were measured. Aerobic endurance was assessed using a graded exercise test on the cycle ergometer. Based on the results of the graded exercise test performed before the training sessions, individual intensity zones for HIIT were determined. Statistical analysis was conducted using Python 3.12.2 documentation software and basic measures of descriptive statistics (mean, SD). The significance level was set at p<0.05. RESULTS: The results showed that none of the applied training models significantly influenced the change in BM (p=0.605) and BMI (p=0.392) among the participants. Statistically significant changes in FM were observed between groups (p= 0.046). In the LLTH group and the LHTL group, a significant decrease in fat mass was observed on average by 2.12kg (SD= 1.06) and 0.74kg (SD= 0.37), respectively. There were no differences in FFM levels between the first and second measurements in the LHTL and C groups. A significant increase in FFM was observed only in the LLTH group (p=0.022). In the C group, no changes in the level of any of the physiological indicators were noted between the first and second measurements. The LHTL group also did not show statistically significant changes in the investigated indicators (HRmax p= 0.164; VEmaxp=0.824; VO2max L/min p = 0.801; VO2max ml/min/kg p = 0.468). Among men in the LLTH group, a significant increase in VO2max L/min (p = 0.026) and VO2max ml/min/kg (p = 0.010) was demonstrated. CONCLUSIONS: In summary, the combination of two stimuli in the form of hypoxic conditions and high-intensity physical training appears to be a promising step towards achieving significant effects in physical endurance and bodyre-composition. Training in hypoxic conditions seems to be a more effective and time-efficient model compared to strategies involving prolonged exposure to hypoxia. Keywords - Physiological Parameters, HIIT, Normobaric Hypoxia, Body Composition